With the recent spread and progress of personal computers, recording and reproduction apparatuses such as hard disk drives have been widely used as external storage apparatuses because of their large capacity and high speed. In order to meet recent increases in the size of computer software and the size of data to be processed, the speed and the capacity have been further improved in these recording and reproduction apparatuses serving as external storage apparatuses.
By virtue of their high speed and large capacity and by using digital technology, such recording and reproduction apparatuses having processed computer data are now used also as digital AV devices or recording and reproducing audiovisual data (referred to as AV data, hereafter).
As a first prior art, described below is a reproduction apparatus capable of performing jumping reproduction.
FIG. 12 shows a reproduction apparatus 102 capable of performing jumping reproduction.
The jumping reproduction indicates that, for example, AV data recorded in a recording medium is reproduced for 15 minutes starting from the beginning of the data, that the AV data from the point at 15 minutes to the point at 25 minutes relative to the beginning of the data is not reproduced, and that the AV data starting from the point at 25 minutes relative to the beginning of the data is reproduced immediately after the reproduction of the data of the 15 minutes starting from the beginning of the data. That is, the term indicates that AV data is reproduced with a predetermined part thereof being skipped.
Another example of the jumping reproduction is as follows. In one example a broadcasted program is recorded into a recording medium starting from the beginning of the program. During this recording, a button (pause button) is pushed which temporarily stops the recording apparatus at the time when AV data has been recorded for 15 minutes starting from the beginning of the program, whereby the recording of the AV data is stopped temporarily. The recording of the AV data is then restarted at the time when the AV data at 25 minutes relative to the beginning of the program is received.
When the AV data recorded in the recording medium as described above is reproduced, the AV data is reproduced for 15 minutes starting from the beginning of the program, and immediately after that, the AV data starting from the point at 25 minutes relative to the beginning of the program is reproduced. Such a case that the AV data, the recording of which is stopped temporarily during the recording is reproduced is also referred to as jumping reproduction.
The reproduction apparatus 102 comprises an HDD 2, stream controlling means 103, an IEEE1394 I/F 4, and a byte counter 101.
The HDD 2 is a hard disk drive of reading and reproducing AV data recorded in a hard disk medium.
The byte counter 101 is a counter of performing the byte counting of the position of AV data outputted as an MPEG transport stream by the stream controlling means 103.
The stream controlling means 103 is means of restoring the time interval of the transport packets of the AV data reproduced by the HDD 2, into the original time interval during the recording, and then outputting the data.
The IEEE1394 I/F 4 is means of providing an MPEG transport stream outputted from the stream controlling means 103, to an IEEE1394 bus which is not shown.
Described below is the operation of the reproduction apparatus 102.
At the start of reproduction, the stream controlling means 103 notifies the start of reproduction to the byte counter 101.
On receiving the notice of the start of reproduction, the byte counter 101 counts reproduction position information as the number of bytes counted from the beginning.
On receiving a reproduction command from the stream controlling means 103, the HDD 2 reads AV data from a location of the hard disk medium corresponding to an LBA (logical block address) specified by the stream controlling means 103, and thereby outputs the data to the stream controlling means 103.
On receiving the AV data from the HDD 2, the stream controlling means 103 restores the time interval of the transport packets of the AV data, and then outputs the data to the IEEE1394 I/F 4.
The IEEE1394 I/F 4 provides the MPEG transport stream outputted from the stream controlling means 103, to the IEEE1394 bus.
On the other hand, after receiving the notice of the start of reproduction from the stream controlling means 103, the byte counter 101 continues the byte counting of the position of the AV data outputted from the stream controlling means 103 to the IEEE1394 I/F 4.
The present value of the byte counter 101 is assumed to be m bytes (m is a positive integer). That is, the AV data in the amount of m bytes has been reproduced already since the start of the reproduction of the AV data.
At that time, it is assumed that the count value of the byte counter 101 is changed from m to n, and hence that an operation command instructing the reproduction apparatus 102 to perform jumping reproduction is received from a remote controller or the like of the reproduction apparatus 102. Then, the byte counter 101 notifies that the count value has been changed from m to n.
In response to this, the stream controlling means 103 outputs a transport packet of the time immediately before the notice from the byte counter 101, to the IEEE1394 I/F 4, then reads the AV data corresponding to the n bytes counted from the start of reproduction, from the HDD 2, and then outputs the beginning transport packet of this AV data corresponding to the n bytes counted from the start of reproduction, to the IEEE1394 I/F 4 immediately after the output of the preceding transport packet.
As such, when the value of the byte counter 101 is changed discretely, the stream controlling means 103 performs jumping reproduction.
In the reproduction of AV data such as a motion picture, the jumping reproduction permits, for example, uninteresting portions to be skipped, and hence interesting portions to be solely watched.
As a second prior art, described below is a reproduction apparatus capable of transiting from special reproduction to normal reproduction.
The reproduction apparatus performs the special reproduction and the normal reproduction of AV data recorded as an MPEG transport stream in a hard disk medium. When the reproduction apparatus transits from special reproduction to normal reproduction, a PCR packet is not always outputted at the start. When video data is outputted before the first PCR packet is outputted, missing of the video data occurs. When the value of PCR is changed from the value of PCR of special reproduction to the value of PCR of normal reproduction, a shock is temporarily occurred in the PLL-control-system which is synchronized with PCR and outputted video and audio is disturbed.
As a third prior art, described below is a method of performing special reproduction in the case that AV data is recorded as an MPEG transport stream in a disk medium or a tape medium.
Described first is special reproduction in a D-VHS.
FIG. 21 shows block diagrams illustrating special reproduction by a D-VHS. FIG. 21(a) is a block diagram showing the case that the D-VHS records an MPEG transport stream into a tape medium 1073. FIG. 12(b) is a block diagram showing the case that the D-VHS performs the special reproduction of the AV data recorded in the tape medium 1073.
Described first is a special reproduction scheme in the D-VHS.
FIG. 21(a) is a block diagram of the recording in the D-VHS.
A transport decoder 1070 of the D-VHS separates an MPEG transport stream to be recorded, and thereby outputs a PES stream.
A PES decoder 1071 receives the PES stream outputted from the transport decoder 1070, and thereby converts the PES stream into an elementary stream.
An I-frame extraction 1072 receives the elementary stream outputted from the PES decoder 1071, and thereby extracts an I frame to be used in the special reproduction.
Further, the I-frame extraction 1072 eliminates the AC components of the extracted I frame, and thereby reduces the amount of data.
The data of the I frame which has been outputted from the I-frame extraction 1072 and the amount of data of which has been reduced is recorded into a special reproduction data region provided in a tape medium 1073.
FIG. 21(b) is a block diagram of the reproduction in the D-VHS.
The data recorded in the tape medium 1073 is read from the tape medium 1073, and then outputted to an I-frame extraction 1074.
From the received data, the I-frame extraction 1074 extracts data read from the special reproduction data region of the tape medium 1073. That is, I frame to be used for special reproduction is extracted. Then, the extracted I frame is outputted as an elementary stream.
A transport stream restoration 1075 receives the elementary stream to be used for special reproduction from the I-frame extraction 1074, then adds a PES header to the elementary stream so as to generate a PES stream, and then generates a transport stream from the PES stream. In the generation of the transport stream, a PAT, a PMT, and an SIT are added. Further added is a special reproduction PCR. The MPEG transport stream generated as described above is decoded and displayed, for example, in a television receiver, whereby special reproduction is performed.
Described next is a special reproduction scheme in a hard disk drive capable of recording and reproducing AV data.
FIG. 22(a) is a block diagram of the recording.
An IEEE1394 interface (not shown) of the hard disk drive capable of recording and reproducing AV data receives AV data transmitted from an IEEE1394 bus or the like.
The IEEE1394 interface outputs the received AV data as an MPEG transport stream to a special reproduction information generating means 1076.
The special reproduction information generating means 1076 analyzes the MPEG transport stream outputted from the IEEE1394 interface, and thereby generates special reproduction information. The special reproduction information comprises the type of picture, position information, and size information. The type of picture is information indicating that a frame is an I, B, or P frame. The picture position information indicates the position where the I, P, or B frame begins, and specifies, for example, the byte where the I, P, or B frame begins relative to the beginning of the AV data. The size information indicates the byte size of the data of the I, P, or B frame.
A formatting 1077 receives the special reproduction information and the MPEG transport stream, and thereby converts the data into a recording format. That is, the formatting 1077 converts the data into a format used when the data is stored into a disk access unit which is a minimum unit for continuous access to a disk medium 1078. The format of the disk access unit comprises a header section and a data section. The MPEG transport stream is stored in the data section, while the header section stores: the special reproduction information such as the type of picture, the position information, and the size information; chain information of specifying the preceding and the following disk access units; and the like.
As such, the data is converted into the format of disk access unit, and then recorded into the disk medium 1078.
FIG. 22(b) is a block diagram of the reproduction.
On the basis of the special reproduction information stored in the header section of each disk access unit out of data read from the disk medium 1078, an I frame cutting-out 1079 cuts out the I frame to be used for special reproduction from the MPEG transport stream stored in the data section of the disk access unit.
The I frame cutting-out 1079 then outputs the cutout I frame as an MPEG transport stream.
Using the PID of the transport packet of the MPEG transport stream received from the I frame cutting-out 1079, a PID filter 1090 eliminates packets other than video packets, and thereby outputs a transport stream composed solely of video data.
The transport packet outputted from the PID filter 1090 and composed solely of video data is then provided with a PAT, a PMT, and an SIT for special reproduction. Further a special reproduction PCR is added. Continuity counter in the header section of each transport stream is rewritten such as to be successive, whereby a complete transport stream for special reproduction is restored.
The restored transport stream is converted into an isochronous packet by an IEEE1394 interface (not shown) and then transmitted to an IEEE1394 bus.
The MPEG transport stream transmitted as described above is decoded by an AV device such as an STB (set-top box), and then displayed, whereby special reproduction is performed.
As a fourth prior art, described below is a method of switching AV data.
FIG. 24(a) shows an example of an MPEG transport stream outputted from an STB which receives an MPEG transport stream broadcasted in a broadcasting wave from a broadcasting station.
In the example of FIG. 24(a), during the time when the STB selects a channel 101 and outputs an MPEG transport stream of the channel 101, another channel 191 is newly selected.
The PID of the video packet of the MEPG transport stream outputted from the STB when the channel 101 is selected is 0x100. In contrast, after the channel 191 is newly selected, the PID of the video packet of the MPEG transport stream outputted from the STB is changed into 0x300. It should be noted that a video packet indicates a transport packet containing video data among the transport packets in the MPEG transport stream. The PID of a video packet is registered in the PMT, and hence the PID of the video packet is obtained by referring to the PMT.
In an AV device such as a television receiver which receives, decodes, and displays the MPEG transport stream outputted from the STB, when the PID of the video packet of the received MPEG transport stream changes, the AV device determines that the channel has been changed, and thereby mutes intentionally the voice and the video for a predetermined time so as to manifest the channel change. In data broadcasting, at the channel change, a browser for the data broadcasting is restarted, whereby the data of the content is renewed immediately. An example of such a browser for data broadcasting is a BML browser corresponding to the BML language.
As such, in an AV device such as a television receiver which decodes and displays an MPEG transport stream, when a change occurs in general in at least one of the PID of a transport packet containing an PMT, the PID of a transport packet containing video, and the PID of a transport packet containing a PCR, the AV device determines that the channel has been changed, and thereby mutes intentionally the voice and the video for a predetermined time so as to manifest the channel change. Besides, at the channel change, a BML browser is restarted, whereby the data of the content is renewed immediately.
Accordingly, when the channel is changed in the STB, the television receiver which receives and decodes the MPEG transport stream outputted from the STB mutes temporarily the television screen. This permits the user to recognize easily the channel change. Further, the restart of the BML browser permits immediate renewal of the data of the content of the data broadcasting.
Nevertheless, in the first prior art, in the timing of receiving the operation command for jumping reproduction, the reproduction apparatus 102 of FIG. 12 stops the reproduction of the MPEG transport stream, and then reproduces the MPEG transport stream at the destination of jumping.
Thus, such a case can occur that the reproduction apparatus 102 stops the reproduction and the output at the time when the transport packets of a frame are outputted midway before the jumping, and that after the jumping, the reproduction apparatus 102 restarts the reproduction and the output at a transport packet in the midway of a frame. Thus, when the MPEG transport stream outputted from the reproduction apparatus 102 is decoded and displayed, a block noise which is specific to MPEG occurs in the jumping reproduction portion.
Further, in the case that after a temporary stop during AV data recording, the recording of the AV data is restarted so that the AV data is recorded in a recording medium, the AV data is interrupted temporarily during the recording at a transport packet in the midway of the transport packets constituting a frame. Then, the recording is restarted at a transport packet in the midway of another frame. Accordingly, when such AV data is reproduced from the recording medium, at the point of the recording interruption, the reproduction is interrupted at a transport packet in the midway of a frame, and then restarted at a transport packet in the midway of another frame.
Accordingly, in each of the above-mentioned cases, a block noise which is specific to MPEG occurs frequently in the jumping reproduction.
That is, there is the problem that in jumping reproduction, when the MPEG transport stream under the jumping reproduction is decoded and displayed, many noises occur in the video and the audio corresponding to the vicinity of the jumping.
In the second prior art, there is the problem that when the reproduction apparatus transits from special reproduction to normal reproduction, missing video data occurs and outputted video and audio is disturbed.
In the third prior art, in the AV data recorded in the D-VHS and the hard disk, such a case can occur that the PID of the transport packet containing a PCR is identical to the PID of the transport packet containing video data.
FIG. 23(a) shows a transport packet 1095 in such a case. A TS header 1092 is a section of the header of the transport packet other than the section of an adaptation field 1093. A PID is described in this section.
The adaptation field 1093 is added to the header of the transport packet 1095 when necessary. A PCR is described in this section.
Video data is stored in a payload 1094.
As such, the transport packet 1095 contains the video data and the PCR simultaneously.
When the PID filter 1090 of the hard disk drive of FIG. 22 is intended to eliminate PCR packets and thereby collect solely video packets using the PIDs of the transport packets, in case that the transport packets are as shown in FIG. 23(a), the PCR packet and the video packet have the same PID and hence are undistinguishable.
Accordingly, when the transport stream restoration 1091 of FIG. 22 adds a special reproduction PCR, the outputted MPEG transport stream is as shown in FIG. 23(b). That is, a new PCR 1096 is a transport packet containing the PCR newly added for special reproduction, while an old PCR/video 1097 is a transport packet containing the PCR and the video data which have originally been added. This causes a mixed state between the PCR newly added for special reproduction and the PCR having originally been added, and hence constitutes an inappropriate MPEG transport stream.
That is, there is the problem that when the PID of the transport packet containing a PCR is identical to the PID of the transport packet containing video data in an MPEG transport stream to be processed by special reproduction, and when an MPEG transport stream for special reproduction is generated from the transport stream, an appropriate MPEG transport stream is not generated.
In the fourth prior art, in case that the AV data recorded as an MPEG transport stream in the recording and reproduction apparatus such as a hard disk and a D-VHS is composed of data generated by editing and joining plural pieces of AV data, the PID of the video packet can change at the joint portion.
FIG. 24(b) shows an MPEG transport stream obtained when such AV data is reproduced by the recording and reproduction apparatus. The MPEG transport stream shown in FIG. 24(b) is generated by editing and joining a stream A and a stream B which are two distinct MPEG transport streams.
The PID of the video packet of the stream A is 0x100, while the PID of the video packet of the stream B is 0x102. The PID of the video packet changes at the portion joining the stream A with the stream B.
Accordingly, when an AV device such as a television receiver decodes and displays the MPEG transport stream shown in FIG. 24(b), even when the user having edited the MPEG transport stream intends that the video and the audio would be displayed continuously as illustrated in FIG. 24(b), the AV device such as a television receiver determines as if the channel was changed at the portion joining the stream A with the stream B, and thereby mutes temporarily the video and the audio displayed through the television screen.
FIG. 24(c) shows a reproduction stream for the case that recording contents are recorded on and reproduced from a disk on an object basis and that the contents are reproduced with switching the object. That is, this stream is an MPEG transport stream for the case that the reproduction is performed across two objects, that is, for the case that the reproduction is performed across an object A and an object B.
However, in the MPEG transport stream of FIG. 24(c) the PID of the video packet dose not change at the joint portion.
Accordingly, when an AV device such as a television receiver decodes and displays the MPEG transport stream shown in FIG. 24(c), the PID of the video packet dose not change, whereby the video and the audio are not muted at the joint portion. Thus, the change of the object is not clear for the person watching the television screen. That is, when the reproduction is performed with switching the object, such an inconsistency occurs that the muting is performed when the video packets have distinct PIDs but that the muting is not performed when the video packets have the same PID.
Further, in case that data broadcasting or the like is reproduced with switching the object, there is the problem that when the PIDs are the same, the browser for the data broadcasting is not restarted, and that the renewal of the browser screen thereby delays.
Further, when analogue broadcasting such as terrestrial broadcasting is received by a terrestrial tuner, and when the analogue signal is inputted to an STB, the STB converts the analogue signal temporarily into an MPEG transport stream, and then outputs the stream to an AV device such as a television receiver which decodes and displays the MPEG transport stream.
In this case, when the STB converts the analogue signal into the MPEG transport stream, a certain PID is assigned to the PID of the video packet.
Accordingly, even when the reception channel is changed in the terrestrial tuner, the PID does not change in the video packet of the MPEG transport stream outputted from the STB.
FIG. 24(d) shows an example of the MPEG transport stream outputted from the STB when the channel is changed in the terrestrial tuner.
The PID of the video packet when a channel 2 is received in the terrestrial tuber does not change even after the channel is changed to a channel 4 in the terrestrial tuber.
Accordingly, despite that the channel 2 has actually been changed into the channel 4, the AV device such as a television receiver which decodes and displays the MPEG transport stream does not determine that the channel has been changed, and thereby does not mute the video and the audio displayed on the television screen.
As a summary of the above-mentioned technical problems in the fourth prior art, first, there is the problem that in case that an edited MPEG transport stream is reproduced, when the portion joining two MPEG transport streams is decoded and displayed, the video and the audio are actually muted despite that the person having edited the stream intends not to mute the video and the audio.
Further, there is the problem that when reproduction is performed with switching the object, such a case can occur that muting cannot be performed at the switching of the object even when the muting is desired.
Furthermore, there is the problem that when data broadcasting is reproduced with switching the object, such a case can occur that the browser for the data broadcasting is not restarted at the switching of the object, and that the renewal of the screen thereby delays.
Furthermore, there is the problem that in case that an analogue signal received by an analogue tuner is converted into an MPEG transport stream and then the converted MPEG transport stream is decoded and displayed, even when the channel is changed in the analogue tuner, the displayed video and audio are not muted.